by Josh Schroeder
When selecting a heat source for your heated platen press application, you should first consider your process requirements followed by the total cost of ownership. In your evaluation there are advantages and disadvantages you should consider for each method of heat transfer.
Heat Transfer (Fluid) Systems
The advantages of a Hot Oil or Heat Transfer System are that it produces the most accurate and uniform temperature control across the surface of the platens. Accuracy is typically from 1 to 5 degrees Fahrenheit depending on the platen design. Process temperature ramping can also be controlled consistently with this type of system and large heat loads are possible. The maximum operating temperature is around 700 degrees Fahrenheit.
Another advantage is that cooling of the platen can also be achieved utilizing the same circulating system. This will allow product to be removed from the press at a safe operating temperature for personnel. This can also be used to provide an end of shift cool down for equipment.
Maintenance of these systems can be considered both an advantage and disadvantage. The heat system is external to the press and therefore routine maintenance and electrical connections can be serviced without disrupting the press. The down side is that the oil is a flammable medium and can be a fire hazard if proper industrial hygiene and preventative maintenance are neglected.
These systems are very accurate and provide uniform temperatures even with large heat loads. The cost for this level of accuracy is much higher than metal sheath style heaters and maintenance of these systems can be demanding but if your process requires tight tolerances these systems are the best choice.
Metal Sheath Insert Heaters
The advantages of metal sheath insert heaters are that they can produce fast heat up and recovery times. They provide efficient energy usage with the heaters inside the platens and can achieve high temperatures up to 1,200 Fahrenheit. The initial cost is also much lower than the hot oil systems and maintenance cost would be considerably less. The risk of fire is greatly reduced as well.
The disadvantages are that temperature uniformity across platen surfaces is not as accurate. The delta range is typically from 15 to 30 degrees. Also the physical dimensions of the platen may limit the amount of KW that can be installed.
Maintenance on these systems is relatively low in comparison to hot oil however should a heater failure occur often the heater must be drilled out of the platen. This may lead to extended downtime.
Metal Sheath Insert Heaters provide efficient energy usage and fast heat up and recovery times coupled with higher temperature capabilities but they do not provide the same level of accuracy or uniformity. If you are looking for a lower cost option and your process does not demand the higher accuracy or uniformity of the hot oil systems then insert style heaters would be the best choice.
by Michael Riehn
I was trying to get my 6 year old son ready for bed the other night when he asked me the innoncent question: “Daddy, what do you do at work?” Now I know he was stalling for time (he’s a normal kid and hates going to bed), but it was a great opportunity to teach him about how things are made.
I explained to him that my company makes big machines called “hydraulic presses”. We help people find the best way to make parts for things that you see every day.
From motorcycles or ceiling lights to airplanes, many parts were built using hydraulic presses. By taking a piece of metal (or composite) and applying force, hydraulic presses make some pretty cool shapes that last.
Obviously, there is a lot more to it, but that gave a 6 year old a concept of what a hydraulic press does (and helped me get him to bed in a reasonable amount of time).
While explaining many of the interesting products that we have worked with, it occured to me how we take for granted how flexible a hydraulic press really is.
From stamping a car door, to punching a light hole or drawing a tank, parts and press requirements can vary quite a bit by changing a few small variables.
Hydraulic Press Applications
A sample of the many applications a hydraulic press can do, shows its diverse flexibility: Blanking, Clamping, Coining, Compacting, Compression Molding, Drawing, Embossing, Forging, Flying Cut-Off, Forming, Heated Platen, Injection Molding (RIM, PIM, etc.), Pad Forming, Powder Compacting, Punching, Spotting, Stacking, Stamping, Steel Rule Die Cutting, Tank Head Forming, Trimming, Tryout, and more.
It sometimes seems like every press that we manufacture is different. That doesn’t mean there aren’t similarities. You may have two presses with the same force requirements and physical size that accomplish two very different things.
Speeds, stroke, control systems and ancillary equipment, (along with size and pressure requirements) are all important when engineering the most efficient press for your application requirements.
The application and tooling should focus the press specification, but your hydraulic press sales engineer can guide you through the process, and use their experience to help you make a better part more efficiently. By custom building the hydraulic press, you can cut down on a lot of wasted cost. You could make high tonnage presses with small beds or low tonnage presses with big beds, for example.
A good hydraulic press sales engineer can help you figure out which “bells and whistles” will make your job easier, with a greater return on investment. They should also find which options are overkill and don’t allign to your needs. Sometimes hydraulic press manufacturing is as simple as an explaination to a 6 year old. It’s about helping people make good parts that last.
by Michael Riehn
Compression molding applications require precise pressure and position, speed control, and parallelism throughout the working stroke.
A hydraulic press, is well-suited for these requirements because of its ability to dwell under pressure for any length of time, vary ram speed, and provide a constant force over a large area—precisely the press characteristics compression molding requires.
In addition, many compression molding applications require large bed sizes but comparatively low tonnage. A hydraulic press bed size can vary independent of tonnage capacity, so there is no need to order a large press with unneeded press tonnage to obtain a large bed size.
Dwell times for composites are typically considerably longer than for metals. A hydraulic press is perfectly suited to maintain energy efficient pressure over an extended dwell period. The press designer can engineer the system with variable volume pumps, accumulators, lock valves, etc, with a multitude of control packages to monitor and manage the system requirements. — anywhere from two to 15 minutes per component. .
The press can be engineered with a sizeable daylight to allow enough space to install both the male and female tooling of large molds. Often times, increased daylight is required to form large contoured panels or shapes inherent in the size and shape of an aircraft or automobile, for example.
Specifications for aerospace, wind turbines, and many automotive components are critical, and even small part defects would create quality problems. A bump cycle capability is a standard typical requirement for forming thermoplastic and composite materials because the materials create gas that must be released. The press closes up on the material, applies some tonnage, then opens a ¼ inch to one inch, and then closes again immediately. Without it, many parts would have large voids in them.
Hydraulic press features that can optimize the compression molding process include control of ancillary process equipment, actuation of internal die components (such as core knockouts, ejectors, and punches), and upacting or multiple-action rams. Precision-heated platen integration with specified heating tolerances and die controls usually are standard.
Additional features such as double- and triple-action rams and part ejection systems can be incorporated into an integrated press system.